The invention relates to a gas compressor of the type which is switchable between operation under load and idle operation, and more particularly, to a gas compressor in which an outlet valve is connected to a pressure relief chamber during idle operation.
A gas compressor of this type is disclosed, for example, in German Patent DE 43 21 013 A1 (corresponding to U.S. Pat. No. 5,503,537, which is incorporated herein by reference). The compressor includes a compression chamber which is connected via a shuttle valve to an additional compression chamber in idle operation. Such design causes an idle self-stabilization pressure to build up in the compression chamber and in the additional compression chamber during idle operation, resulting in the elimination or reduction of the gas compressor's oil consumption.
The output quantity of such a gas compressor is controlled by means of a pressure regulator, used alone, or together with other control devices. In idle operation, the pressure regulator disconnects the output of the outlet valve of the gas compressor from the pressure system to be supplied and connects this output to a pressure relief chamber which is under atmospheric pressure. The pressure regulator is normally installed in a line system interconnecting the outlet valve with the pressure system or the pressure relief chamber.
In order for a build-up of pressure in the above-mentioned compression chambers to be rendered at all possible while in idle operation, the outlet valve must be disabled in idle operation. This is effected by a first shuttle valve. Furthermore, the first shuttle valve allows the gas compressor to operate with pre-compressed gas. Such applications are common in the automotive industry, in which air is the gas used. In this technical field, the usual practice is to feed the air to be compressed to the gas compressor from the suction line of the combustion drive engine. To increase the engine output, the air fed to the engine, and thereby also to the compressor through the suction line, is often pre-compressed (super-charged). The gas used in other technical fields is also mainly air. In such cases where air is the gas used, the atmosphere generally serves as the pressure relief chamber.
As a consequence of disabling the outlet valve in idle operation, no flow takes place in idle operation between the compression chamber and the pressure relief chamber. This lack of flow may lead to an accumulation of pollutants and liquid from the gas, as well as to freezing, and may thereby contribute to malfunctions in the components which are between the compression chamber and the pressure relief chamber, such as the outlet valve, lines, and pressure regulator.
It is therefore the object of the invention to further develop a gas compressor of the type mentioned above in a simple manner such that malfunctions caused by disabling the outlet valve may be avoided.